Psychrometer



Aug. l0, 1943. 1. cRAPl-:z

PSYCHROMETER Filed .my fr, 193s INVENTOR JULES CRAPEZ m/.f ATTORNEYSPatented Aug. 10, 1943 PSYCHROMETER Jules Crapez, Mons-en-Baroeul,France; vested in the Alien Property Custodian Application July 7, 1939,Serial No. 283,196 In France July 16, 1938 (Cl. 'Z3-338) I 4 Claims.

This invention relates to an improved psychrometer, and tne object ofthe invention is to provide a direct reading psychrometer in whichreadings can be takenimmediately so as to obtain the hygrometric degreeoi any atmosphere without having to read, or know-the readings of a drybulb thermometer and a wet bulb thermometer, and without having to makeany calc'ulation.

This object is completely attained by the psychrometric device describedbelow, which comprises a special arrangement of a dry bulb thermometerand a wet bulb thermometer, with a mechanical means foractuating arectilinear rod which can be aligned with the meniscuses formed by thetwo levels of thethermometer columns so as to indicate on a scalegraduatedfor this purpose the corresponding hygrorr'ietric` degree.

In addition, this device has the advantage that it can be made speciallysuitable for a given range of hygrometer readings by varying therespective positions of the thermometer scales of the dry bulb and wetbulb thermometers, both by the relative dimensions of their graduationsand by the'distance separating the two thermometers.

Figures l to 6 of the accompanying drawing show by way of example oneembodiment of the invention and the manner of carrying it out inpractice.

Figures 1 to 3 explain technically the conditions required forconstructing one of these types of psychrometer.

Figures 4 toV 6 show an elevation, profile and plan View respectively ofapparatus constructed for industrial requirements.

Referring to said drawing, Figure 1 shows two thermometers I and 2placed at a certain distance D from one another.

The length of the scale of the thermometer 2 is less than the length ofthe scale of the thermometer I. The bulb of thermometer 2 which is thewet bulb thermometer is maintained permanently moist. The highestgraduations of each of the two thermometers which here are assumed tohave the same thermometric value, are placed at the same level. y

A screw 3 actuating a nut 4 provided with a projection 5 supports a rod6 which can turn freely on said projection.

r*Another screw I actuates a nut 8 which likewise carries a projectionsuch as 9, on which rests the other end of the rod 6 which may or maynot be supported in a catch.

The rod 6 moves in front of a scale graduated according to a table ofhygrometric degrees for psychrometer reading. If by operating the screws3 and I the rod 6 is aligned with the tops I0 and II of the meniscusesof the dry bulb and wet bulb thermometer columns, this rod likewisepassesthrough the point I2 of the scale representing the hygrometricdegree sought;

In effect, suppose that the previous position corresponds to a givenhygrometric degree. Now suppose rod 6 to be moved to a second position6', with positions I3 and I4 of the meniscuses corresponding to the samehygrometric degree represented by the point I2- If N1 is the number ofdegrees between the two positions I0 and I3, and N2 the number ofdegrees between the positions I I and I4, and if on the yother hand L isthe distance from the point I2 to the thermometer 2, we have: l

iif 1) Now, if the tables for determining the hygrometric degree areconsidered these tables being prepared on the basis of the number ofdegrees of the wet bulb thermometer plotted as ordinates and thediierence between the degrees shown on the dry bulb thermometer and thewet bulb thermometer plotted as abscissae, it is noticed that all thevalues of the same hygrometric degree are aligned. Let us assume,therefore, one of these tables and the indication of the valuescorresponding to II and I4 previously taken as an example for the wetbulb thermometer. The values of the hygrometric degree H and H1represented by the point I2 on the scale of the apparatus are alignedand cut at 0 the axis showing the readings of the wet bulb thermometer(see Figure 2). If Th1 and Th2 represent the numbers of absolute degreesbetween the point of intersection D and the point representing the wetbulb temperatures, and if El and E2 are the diiierences between the wetbulb thermometer Th and the dry bulb thermometer Ts, according to thesetables and for the same hygrometric degree we can write:

Y hygrometric degrees... v

In eiect, if at Vthe maximum dry temperature` is therefore ccnstant'anclequal to the general ratio deducted-from the tables of readings. Y

therefore there is a single valueo L.

Inorder to'be able to integrate the scale bearapertures Band B' forallowing access/of air to the thermometers and apertures C for lookingat the level of the water inthe tank. This frame receives in suitablerecesses thermometers l and 2, namely the dry bulb thermometer and thewet thermometer, the bulb of the latter being provided with a piece ofmuslin' M dipping into a ,container such as J which islsuitablymaintained Y in place whilefbeing capable oi easy removal for refillingit with distilled water. i

A As can be'as'certained, the thermometers I and 2 have Vdifferentlengths of graduations, but in this particular construction the highestgraduing'the indications of the different values of the hygrometricdegreewithin given limits, the value of the graduations of the wet bulbthermometer are reduced in the ratio K, this ratio being greaterthanrunity. Y Y f lThis fact does not alter the equality of the previousVratios which become:

el 're .n

Y VBy reducing Tm N2 is reducedl in the same 1atio.r ,Y f Y On theotherrhand Equation 1 can be written:

- f DNz V j if N2 is reduced in the ratio r; we Yshall have:

me Y

As K is greater than 1, it is clear that by reducing N2,Lwill bereduced. j l j' It Yhas been stated that this psychrometer can be usedfor taking readings with increased accuracy in some particular region ofthe scale of for which the dryV bulb thermometer has been designed thereis aligned horizontally with this dry division the maximum'graduation cia wet Ybulb thermometer lower than the Ytemperature a ofthe dry bulbthermometer, it follows that on this horizontal `line there will bealigned'a point of thescale of hygrometric degrees indicating a valuebelow thef saturation point, since for this value aligned on'thehorizontal there is a Adifference between fthe readings of the dry bulband 'wet bulb thermometers,

This value of the hygrometricpdegree corre,- sponds at thismoment togiven indi-cations obtained by a substantially horizontal position ofthe rod 6" (see Figure 3) which corresponds to the maximum accuracy ofreading with a size of thermometer for the range of readings to beeffected.

a much larger psychrometer.

Anexample of an'apparatus constructedaccording to these data is shown inFigures 4to 6,

This modified apparatus corresponds in fact to from which yit will beseen that the psychrometer comprises a frame A forming a casing withenlargement VA' for accommodating the water tank,

ations are placed at the same level. The frame -A inthe form of a casingencloses screws V and 9V' "having milled operatingknobs 3 andi. Thescrew V guidedY at 3 at its lcwerpart carries a this purpose one of`itsends is pivotally mounted on the projection 5, and theother free endrests on the projection and is guided Yor retained in a small catch (notshown in the drawing).

It will be understood that under these conditions it will-,be sufficientto actuatethe two milled knobs 3 and l in order to bring E tothe levelof thetwo thermometer columns and to read on the scale G the hygrometricdegree corresponding to these two levels. y v

YAs canfrbe understood thisapparatus is very simple, its mechanismcannot get out'of order and on account Vof the arrangement of the twothermometers which could `be varied as stated it becomes possibletofspecify certaintypes of apparatus for rdifferent well dened ranges ofread- Y ings, said types of apparatus being consequently suitable forthe requirements of some industry or other. Y

I claim :v Y

l. A direct reading psychrometer comprising in Vcombination a support, adry bulb'thermometer ber. with the meniscuses of the thermometer collumns the hygrometer rscale beingr so related to the rectilinear rod whenin registry' with the meniscuses of the indicating columns of thethermometers that the rod intersects the scale tofgive a lcorrectreading of the hygrometric state of thev atmosphere being measured. 1

2. A direct reading psychrometer comprising in combination a support,afdry bulb thermometer and a wet bulb thermometer both of the mercurytype `spaced parallel to each otherand mounted on said support, ahygrometer scale on said support, a rod or equivalent member, movablemembers supporting said rod'or Yequivalentmember, au vertical guide andan obliquely inclined: guide for said movable members, and screw meansfor adjusting said rodror equivalent member to align it with the tops ofthe thermometer columns, the

hygrometer scale being so related to the rectilinear rod when inregistry with the meniscuses of the indicating columns of thethermometers that the rod intersects the scale to give a correct readingof the hygrometric state of the atmosphere being measured.

3. A direct reading psychrometer comprising in combination a support, adry bulb thermometer and a Wet bulb thermometer both of the mercury typespaced parallel to each other and mounted on said support, a hygrometerscale on said support, a rod or equivalent member, two

sliders, on one of which said rod or equivalent member is pivotallymounted while the other acts as a rest, a vertical guide and anobliquely inclined guide for said two sliders, and separate screw meansfor adjusting the positions of said two sliders to align said rod orequivalent member with the tops of the thermometer columns, thehygrometer scale being so related to the rectilinear rod when inregistry with the meniscuses of the indicating columns of thethermometers that the rod intersects the scale to give a correct readingof the hygrometric state of the atmosphere being measured.

4. A direct reading psychrometer comprising in combination a support, adry bulb thermometer mounted on said support, a wet bulb thermometeralso mounted on said support parallel to the dry bulb thermometer andgraduated in shorter lengths per degree than said dry bulb thermometer,both thermometers being of the mercury type, a hygrometer scale mountedon said support, a slot adjacent said dry bulb thermometer and a secondslot extending at an acute angle to the rst slot and situated adjacentsaid hygrometer scale, sliders movable in said slots, a rod pivotallymounted on one of said sliders and freely supported by the other slider,and separate screw means for raising and lowering said slidersindependently, the hygrometer scale being so related to the rectilinearrod when in registry with the meniscuses of the indicating columns ofthe thermometers that; the rod intersects the scale to give a correctreading of the hygrometric state of the atmosphere being measured.

JULES CRAPEZ.

